GSoC [early debugging] Bridging the gap

ARM is now on the table, as I am bridging the coreboot console from USB to gigabit ethernet, using a BeagleBone board equipped with the USB debug device gadget driver. At first I was a bit concerned of all the latency having an USB-to-ethernet bridge software solution on the communication, so it was now good time to do some measurements.

I used daemon called ser2net to redirect coreboot console TTY to TCP (telnet) and enabled timestamping to estimate the time it takes from power-on to entering payload on amd/persimmon with maximum logging (level=spew).

First, connecting with serial UART @115200bps on x86 host this was total of 15 seconds. Of this it spent 4 seconds in AGESA doing some SPI flash operations and during that time there was no console output.

Repeating same using usbdebug on the BeagleBone OTG port, total time was 9 seconds and again 4 seconds was waiting for SPI completion.  I would say we have a rough figure that console output on usbdebug is twice as fast as what super-IO can typically offer.

Driver compilation and patches are updated here:

To use BeagleBone some additional work was needed on coreboot side but BeagleBone Black and other ARM boards where there is no hub between OTG connector and controller should already work.